Polymers obtained by a ring-opening polymerization of cycloolefin monomers that have a norbornene moiety (cycloolefins) are well known. For example, U.S. Pat. Nos. 4,136,249, 4,178,424, 4,136,247 and 4,136,248, assigned to the same assignee as the present invention, describe such polymers and each is incorporated herein by reference for the description of polymers therein.
Depending on the specific cycloolefins chosen, ring-opening polymerization of cycloolefins yields unsaturated linear, branched and crosslinked polymers. They are known to exhibit attractive property profiles for many polymer applications, such as, automotive and non-automotive body panel parts, equipment housings, furniture, window frames and shipment dunnage.
Dicyclopentadiene, for example, is a common cycloolefin monomer used to prepare ring-opened polymerized polymers in that these cycloolefin monomers are readily available as by-products in ethylene production. Recent U.S. patents directed to dicyclopentadiene polymers include U.S. Pat. Nos. 3,778,420, 3,781,257, 3,790,545, 3,853,830, 4,002,815 and 4,239,874. Other well known cycloolefin monomers include bicyclic norbornene (bicyclo[2.2.1]-hept-2-ene) and substituted bicyclic norbornenes, which are produced by Diels-Alder reaction of cyclopentadiene with selected olefins. U.S. Pat. No. 3,074,918 describes the polymerization of cycloolefin monomers including bicyclic norbornene and substituted bicyclic norbornenes, as do other U.S. patents such as U.S. Pat. Nos. 3,546,183, 2,721,189, 2,831,037, 2,932,673, 3,330,815, 3,367,924, 3,467,633, 3,836,593, 3,879,343 and 4,020,021. The above patents are incorporated herein by reference for their disclosure of polymers obtained from ring-opening polymerization of bicyclic norbornenes and substituted bicyclic norbornenes.
Tetracyclododecene and substituted tetracyclododecenes are also well known cycloolefins. These are made by Diels-Alder reaction of cyclopentadiene with bicyclic norbornene or the appropriate substituted bicyclic norbornene. Ring-opening polymerization of tetracyclododecene with other cyclic olefin comonomers (bicyclicnorbornene and substituted bicyclicnorbornenes) has been disclosed in U.S. Pat. No. 3,557,072, incorporated herein by reference for the polymerizations disclosed therein.
Ring-opened polymers and copolymers of dicyclopentadiene and tetracyclododecene are known to have excellent glass transition temperatures (Tg). Because of their high Tg values, these polymers are difficult to melt process once formed. Crosslinking in the melt also occurs when the ring-opened polymer or copolymer contains a pendant five member unsaturated ring such as results when dicyclopentadiene is used to form the polymer or copolymer. Crosslinked polymers are extremely difficult to melt process. This poses a significant disadvantage to solution polymerized polymers which must be melt processed to provide finished articles. In contrast, for polymers and copolymers prepared in bulk, processing, in terms of melt flow, is less of a problem since the polymerization takes place in a mold and in the shape desired. Melt processing for such bulk polymerized polymers and copolymers is normally not required. Therefore, bulk polymerization provides significant advantages where high temperature resistance is desired in the finished article.
Solution polymerization of cycloolefins is accomplished in the presence of (1) a solvent and (2) a metathesis catalyst comprising at least one alkyl aluminum halide cocatalyst and at least one tungsten or molybdenum compound as catalyst. In contrast, bulk polymerization is defined as polymerization in the absence of a solvent or diluent.
Early attempts at the bulk polymerization of cycloolefins using the metathesis catalyst systems of solution polymerization ended in failure because the polymerization reactions were too rapid in the absence of solvent and therefore, uncontrollable. Furthermore, initial bulk polymerization attempts resulted in materials that were very dark, had poor physical properties and poor appearance.
Further developments in the bulk polymerization of cycloolefins led to another approach, which, likewise, was unsuccessful. This approach was characterized by splitting the monomer charge into two equal portions, one containing the catalyst and the other containing cocatalyst. The object was to mix the two portions of the monomer charge at room temperature and then transfer the mix to a heated mold where polymerization and hardening would occur very quickly. It was discovered that instantaneous reaction took place upon contact of the two portions (pre-gellation), whereby a polymer barrier was formed between the two portions of the monomer charge, encapsulating some of the monomer from each portion which prevented mixing.
Minchak describes a modified catalyst system in U.S. Pat. No. 4,426,502 which serves to control the instantaneous reaction between the two portions of the monomer charge, one containing catalyst and the other containing cocatalyst, which permits adequate mixing of these two components without encapsulation.
While the catalyst systems of Minchak provide adequate control over the bulk polymerization reaction, there are other obstacles the manufacturers of molded articles must face. For example, if such a manufacturer is to take advantage of a bulk polymerization reaction of cycloolefins, it is necessary to ship and store the reactive monomers. While it is known the two components of the reactive formulation can be prepared from the reactive monomers both rapidly and efficiently, it is preferable that the monomers be provided with all the necessary additives and catalyst components so that the manufacturer can avoid additional processing and perform bulk polymerization in a single operation.
To achieve this, the reactive monomers are preferably provided in two components, one component containing cycloolefin monomer, cocatalyst, and optionally, a halometal activator, and the other component containing cycloolefin monomer and catalyst. It has been found that some metathesis catalysts, such as molybdenum and tungsten halides do not provide stable mixtures with cycloolefin monomers. The ammonium molybdate and ammonium tungstate catalysts and the alkylalkoxy aluminum halide cocatalysts described by Minchak in U.S. Pat. No. 4,426,502, when separately mixed with cycloolefin monomers alone, have been found to exhibit better than average storage stability when compared to mixtures containing other metathesis catalysts. However, where there is a desire to "activate" the cocatalyst to increase the degree of monomer conversion to polymer in bulk polymerization, it has been found the stability of such mixtures can be lost. This instability can be manifested by changes in color, an increased viscosity, gel formation or loss of catalyst activity. Often these symptoms are due to reactions taking place with certain additives. For example, impact modifiers containing unsaturated carbon atoms are believed to react in the presence of hydrogen chloride to cause the impact modifier to crosslink and thus causes the cocatalyst mixture to become viscous or gel. In certain circumstances, stability problems can be avoided by the proper selection of additives. However, restricting the additives utilized limits the versatility of products obtained.
This invention provides a storage stable cocatalyst component of a reactive formulation, such component comprising at least one cycloolefin monomer containing a norbornene group and a halometal activated metathesis cocatalyst. Methods for producing these storage stable components are also provided. Reactive formulations obtained from this cocatalyst component and a metathesis catalyst component polymerize into hard objects in a single step by means of reaction injection molding (RIM), resin transfer molding (RTM), liquid injection molding (LIM), or other bulk polymerization process.